Reye’s Syndrome Warning Signs: Liver Failure and Brain Swelling Following Viral Illness

Reye’s syndrome is a rare but serious condition that can cause sudden injury to the liver and swelling in the brain. It most often affects children and teenagers while they are recovering from a viral infection such as influenza (the flu) or chickenpox. Symptoms may worsen quickly, even when the original viral illness seemed to be improving.

The strongest known association is between Reye’s syndrome and giving aspirin or other medicines containing salicylates to children or teenagers during or soon after a viral illness. Because of this risk, health authorities generally advise avoiding aspirin in anyone under 18 or 19 unless a doctor has specifically prescribed it.

Reye’s syndrome is uncommon, but it is a medical emergency. If a child or teenager develops repeated vomiting, unusual sleepiness, confusion, seizures, or changes in behavior after a viral illness—especially after taking aspirin—seek emergency medical help immediately.

What is Reye’s syndrome?

Reye’s syndrome can affect several organs, particularly the liver and brain. The liver may stop processing fats normally, leading to a buildup of fatty substances and harmful chemicals such as ammonia in the blood. These chemicals can affect the brain and cause swelling, known medically as cerebral edema.

The condition does not usually cause liver failure symptoms such as yellow skin at the beginning. Instead, the earliest warning signs may look like a stomach bug or a child who is simply very tired. This is why changes in alertness, behavior, or vomiting after a viral illness should be taken seriously.

Reye’s syndrome is not the same as a typical side effect of aspirin, and it is not something that can be safely assessed at home if serious symptoms are present.

Reye syndrome symptoms after taking aspirin

The symptoms of Reye’s syndrome often appear several days after a viral infection begins to improve. They may develop after aspirin use, but not every child exposed to aspirin develops the condition, and Reye’s syndrome can rarely occur without a clear history of aspirin use.

Early symptoms can include:

• Repeated or persistent vomiting
• Unusual tiredness, weakness, or lack of energy
• Irritability or sudden changes in mood
• Difficulty staying awake
• A child who seems less interested in normal activities
• Confusion or trouble answering simple questions
• Loss of coordination or unsteady walking

Vomiting that continues or is accompanied by increasing sleepiness is particularly concerning. A child with Reye’s syndrome may appear well between episodes at first, but their condition can deteriorate over hours.

Warning signs of brain swelling

As brain swelling progresses, symptoms may become more obvious and severe. Emergency warning signs include:

• Increasing confusion or disorientation
• Unusual behavior, agitation, or aggression
• Severe drowsiness or difficulty waking
• Slurred speech or trouble understanding language
• Weakness or loss of coordination
• Double vision or other changes in vision
• Seizures
• Fainting or loss of consciousness
• Abnormal breathing
• A limp, unresponsive, or rapidly worsening child

Call emergency services immediately if a child has a seizure, cannot be awakened normally, has trouble breathing, collapses, or becomes unresponsive. Do not wait for a routine appointment or attempt to manage these symptoms with food, fluids, or additional medicine.

Possible signs of liver injury

Liver problems may occur with or without obvious yellowing of the skin or eyes. Possible signs include:

• Persistent vomiting
• Low blood sugar, which may cause sweating, shaking, weakness, or confusion
• Easy bruising or unusual bleeding
• Severe weakness
• Increasing sleepiness or confusion
• Yellow skin or eyes
• Dark urine or unusually pale stools
• Pain or swelling in the upper right side of the abdomen

Some of these symptoms can have many causes, including dehydration or another infection. However, when they occur after a viral illness and are combined with changes in alertness or behavior, urgent assessment is needed.

Why aspirin is a concern

Aspirin is also called acetylsalicylic acid. It may be found in some prescription and over-the-counter products used for pain, fever, inflammation, or stomach upset. Other salicylate-containing products include some medicines made with bismuth subsalicylate.

Children and teenagers should not be given aspirin during or soon after a viral illness unless a qualified healthcare professional has specifically instructed you to use it. This includes illnesses such as flu, chickenpox, and other infections that may be caused by a virus. Check medicine labels carefully, because aspirin may not always be prominent in a product’s name.

Aspirin may be prescribed to some children for specific medical conditions, such as certain heart or inflammatory disorders. In these cases, do not stop the medicine without speaking to the prescribing doctor. The doctor will weigh the benefits and risks and explain what to do if the child develops a viral illness.

For fever or pain, ask a doctor or pharmacist which medicine and dose are appropriate for the child’s age, weight, and medical history. Never use adult products or combine medicines without checking the active ingredients. Acetaminophen (paracetamol) is commonly used in children, but it can also cause serious liver injury if too much is taken, so dosing instructions must be followed carefully.

When to seek medical help

Speak to a doctor promptly if a child or teenager has repeated vomiting, unusual sleepiness, behavior changes, or confusion after a viral illness. Tell the clinician:

• Which viral illness symptoms occurred
• When the illness started and began improving
• Every medicine or supplement given
• The exact product names and doses
• When aspirin or a salicylate-containing product was taken
• Whether vomiting, confusion, or drowsiness is getting worse

If symptoms are severe or rapidly progressing, go to an emergency department or call emergency services. Do not drive an unresponsive or seriously confused child yourself if emergency transport is available.

You might consider a free, online symptom check, using the doctor approved Ubie Symptom Checker for general guidance about symptoms. However, an online symptom checker cannot diagnose Reye’s syndrome or rule out brain swelling or liver failure. It should never delay emergency care or replace speaking to a doctor about anything that could be life-threatening or serious.

How Reye’s syndrome is diagnosed and treated

There is no single test that confirms Reye’s syndrome immediately. Doctors may use blood tests to check liver function, blood sugar, ammonia, clotting, and other chemical levels. They may also perform imaging or a spinal fluid test when needed to look for other causes of brain symptoms. In some cases, tests are used to exclude conditions such as meningitis, severe infection, poisoning, metabolic disorders, or other causes of liver failure.

Treatment takes place in a hospital, often in an intensive care unit. Care may include monitoring brain pressure, supporting breathing, correcting low blood sugar or abnormal blood chemistry, managing seizures, and treating bleeding or fluid problems. Early treatment offers the best chance of preventing permanent injury.

Prevention and key points

Reye’s syndrome is rare, and most children with a viral illness will not develop it. Still, prevention is important:

• Do not give aspirin to children or teenagers with a viral illness unless a doctor specifically prescribes it.
• Check labels for aspirin, acetylsalicylic acid, and salicylates.
• Ask a pharmacist before giving a combination cold, flu, or stomach medicine.
• Keep medicines out of children’s reach.
• Seek urgent help for repeated vomiting plus confusion, unusual sleepiness, seizures, or worsening behavior.

The most important message is simple: after a viral illness, a child who develops vomiting and changes in alertness needs prompt medical attention—especially if aspirin or another salicylate-containing medicine was used. Speak to a doctor immediately about symptoms that may be serious or life-threatening.